How MICS was Born? Where are We Now?1

One of the latest crucial breakthroughs in phaco-emulsification has been to perform the phacoemulsification surgery through a microincision with a bimanual approach, using a sleeveless phaco tip. Co-axial MICS, as we know today, did not evolve directly from standard phacoemulsification, even that phacoemulsification was described since the early years as a coaxial procedure. Bi-axial technique was born from the idea of performing a less invasive technique in comparison to standard phacoemulsification; this idea leads to the creation of bimanual techniques, currently known as Bi-axial techniques. From this evolution of techniques leading by Biaxial procedures, the idea of performing the same through coaxial was started. Co-MICS is currently a byproduct of Bi-MICS, in particular for those surgeons that did not want to pass through the change process from coaxial to biaxial phaco, it means, the learning curve.

The idea of removing the crystalline lens through two microincisions has been proposed since 1985 by Dr. Steven Shearing, MD in Las Vegas USA, as he propounded the separation of ultrasound/aspiration and the irrigation hand piece; it means like the pars plana vitrectomy procedures.^1,2 However, it was not until that independently Agarwal in India and Tsuneoka in Japan began that technique in 1998 and 1999, respectively, that it gained popularity. Although it is still practiced by a small percentage of the world's surgeons, authors hope that its benefits can be slowly understood.^3,4

Agarwal coined the term “Phakonit” (as you will see in the chapter written by him in this textbook), which initially stood for phacoemulsification (phaco) performed with a needle opening (N) via an ultra small incision (I) with the sleeveless ultrasound tip (T). Originally, Agarwal described an incision as small as 0.9 mm, using a standard sleeveless Microtip. Although initially the theoretical possibility of a possible thermal burn was a concern, this fear was dispelled by several studies. Tsuneoka showed experimentally in a porcine eye that using a sleeveless ultrasound tip, the temperature of the cornea at the incision elevated only 8.4°C without developing thermal burns. In other experiments, Olson et al. demonstrated that clinically unusual parameters were necessary to produce a wound burn in bimanual phaco and moreover, when using “cold phaco” with a bare 19-gauge aspiration needle in human cadaver eyes, a wound burn could not be produced at the highest energy settings unless all flow into the eye and all aspiration were occluded. These settings are well beyond clinically applicable conditions.^5-7 The authors' explanation is that it is difficult to completely occlude a linear stab incision with a metal circular instrument, unlike the situation in standard coaxial phaco, where a flexible irrigation sleeve fills the wound and reduces the flow around the sleeve, particularly in a tight wound.

The sleeveless phaco needle has been a terrible fear for many surgeons to move from coaxial to biaxial phacoemulsification.

The combinations of a tight wound, filled by a flexible irrigation sleeve, and complete occlusion of aspiration, and therefore complete blockage of irrigation results in a wound burn. So in fact, the risk of thermal burn may be less in phakonit than in coaxial phaco.

Agarwal initially reported 305 eyes that underwent the technique successfully.^3,6,7,9 He had the assistant continuously 4pouring cooled balanced salt solution (BSS®) over the phaco needle. The original incision had to be enlarged in order to implant the intraocular lens (IOL). No one case of thermal wound occurred. Tsuneoka and coauthors also initially reported 637 cases that underwent cataract surgery through a 1.4 mm incision without a case of thermal burn.⁴ Likewise the authors of this chapter, working in different surgical centers and for almost a decade of performing all our cataract surgeries under this basis, have not found any single case of corneal wound burn in our patients.

Around the world several other surgeons, including the author of this chapter, have reported their results using bimanual microincision surgery with different phaco machines.

Jorge Alió coined the term Microincision Cataract Surgery (MICS), as you will be able to see in this textbook in the chapter written by him. At that time he reported good visual performance of two available IOLs, which may be implanted through microincisions. In a prospective randomized consecutive case series, he reported that microincision cataract surgery significantly lowered mean phacoemulsification time, mean total phacoemulsification percent, mean effective phaco time and surgically induced astigmatism when compared with coaxial phacoemulsification. Howard Fine has highlighted the advantages of maintaining a more stable intraocular environment during lens removal,¹ as you also will be able to read in the chapter written by him in this textbook. This advantage may be especially important in high myopia, patients who are at a greater risk for retinal detachment following lens extraction or high hyperopes with shallow anterior chamber, decreasing the possibility of an expulsive hemorrhage.

In 2002, Olson was the first to use a 0.8 mm phaco needle and a 21-gauge irrigating chopper in bimanual cataract surgery and called this technique microphaco.

These techniques of performing phacoemulsification through incisions around 1.0–1.5 mm have been spreading around the world. Other names given to these techniques are bimanual phacoemulsification and sleeveless phaco.^2,5,8 Recently, Agarwal reported the microphakonit, a similar technique, but using a 0.7 mm needle and a 0.7 mm irrigating chopper through a sub 1 mm incision. Many chapters in this textbook, including one written by Agarwal himself, talk about the performance of 700 micron cataract surgery, currently the smaller possible incision size for lens removal.

Currently definitions describe that standard coaxial phacoemulsification can be performed through a 2.8–3.2 mm incision. Other techniques that use smaller incisions include micro-coaxial phacoemulsification, which uses a 1.8–2.2 mm incision, and biaxial MICS, which uses a 1.2–1.4 mm incision. In micro-coaxial phacoemulsification, irrigation, aspiration and phacoemulsification are performed with the same instrument (phaco handpiece), used in standard coaxial phacoemulsification. The only difference between the two techniques is the smaller main incision in micro-coaxial phacoemulsification, which is the result of the development of the phaco tip sleeves. In biaxial MICS, however, the irrigation and phacoemulsification aspiration steps are separate; an irrigation chopper is used for irrigation and a sleeveless phaco tip for aspiration and phacoemulsification. Micro-biaxial (or bimanual microphacoemulsification) is named to biaxial techniques performed through 700 micron instrumentation.

Going from a 0.9 mm phaco needle to a 0.7 mm needle diminished the aspiration flow rate, the holding power and in general the efficiency of the tip. So in order to have a feasible procedure, a modified 30 degree tip was developed by MicroSurgical Technology Inc. (MST) Redmond, USA, with thinner walls, allowing for an increased inner diameter thereby increasing efficiency close to that of a 0.9 mm tip. Agarwal uses his end-opening sharp irrigating chopper and gas forced infusion, initially he employed an external air pump⁹ and then the anterior vented gas forced infusion (AVGFI) system of the Alcon's Accurus equipment,⁸ with the infusion pump preset to 100 mm Hg. Authors have already published results with a phakonit technique through 1.2–1.5 mm, using the 20 gauge Microtip, or 19 gauge Standard or MicroFlow® tips. Now Surgeons have available a specially designed 0.7 mm Nanotip (MST), which allows them to perform the surgery through 0.8 mm incision. Because of the good results of these techniques, authors are using it in all their adult and pediatric cataract patients.

When microincisional techniques were born in a biaxial approach, some kind of skepticism by the side of the coaxial surgeons, the fear of corneal thermal burns and the need to avoid the learning curve from coaxial to biaxial, encouraged the industry to the micro-coaxial techniques, leading the creation of smaller phaco tips and smaller phaco sleeves. It has become part of the history of cataract surgery the communication (an electronic mail) from Prof. A Akahoshi from Japan, to the Alcon engineers, asking for new micro-coaxial instrumentation (tips and sleeves) based upon the growing enthusiasm of the cataract surgeons over biaxial techniques; the idea was to make smaller incisions in the very well known, ‘coaxial mode'. Formany surgeons this way microcoaxial technique was born. So all the new instrumentations, the new softwares, the new 5machines, the new methods of IOL implantation and the new models of IOLs that were born for micro-coaxial (and that are described in this textbook) were born from this inquiry of the coaxial surgeons based upon the new biaxial techniques. This is why authors can say that Co-MICS is a byproduct of Bi-MICS, created by a group of surgeons and the industry, for those surgeons that do not desire to go upon the hill of the learning curve of biaxial.

Authors are agreeing with the reports of Arshinoff and Grabow,^10,11 regarding the term biaxial and coaxial to describe the differences between both methods of phacoemulsification performed at this time, according to the axis of the incoming fluid to the eye. Arshinoff wrote these words in the article of Journal of Cataract & Refractive Surgery (Volume 31, Issue 4, Page 646, April 2005) as follows: